System for indicating tension in strip between stands of a multi-stand rolling mill



Jan. 11, 1966 A. J. HULLINGER 3,228,241

SYSTEM FOR INDICATING TENSION IN STRIP BETWEEN STANDS OF A MULTI-STAND ROLLING MILL Filed March 6, 1963 /4 l4 l3 [3 SHUNT msawzime I NETWORK Fi: -l9' --/9 l9a' f-l9a DIFFERENTIAL 7 f VOLTMETER/ T T INVENTOR.

ARV/IV .1. HULL/NGER By W A Horney United States Patent SYSTEM FOR INDICATING TENSION IN STRIP BETWEEN STANDS OF A MULTI-STAND ROLL- ING MILL Arvin J. Hullinger, Utah County, Utah, assignor to United States Steel Corporation, a corporation of New Jersey Filed Mar. 6, 1963, Ser. No. 263,201 2 Claims. (Cl. 73-143) This invention relates to the rolling of metal strip in a continuous or multi-stand mill and, in particular, to a system for indicating the tension applied to a strip bar between successive stands of a hot-rolling mill.

The significant effect of interstand tension on the reduction of steel strip by cold-rolling has long been recognized. The control of interstand tension during the hotrolling operation, however, has received but little attention until recently. It is common practice to attempt to control the speeds of the several stands of a hotrolling mill so that the tension between stands will be a minimum, because such condition contributes dimensional quality to the finished product. It is difficult to achieve this objective, however, because of the lack of means for indicating the interstand tension for the guidance of the operators.

I have invented a system for continuously indicating the interstand tension on a strip bar passing through a hot-rolling mill, without the necessity for making contact with the bar. The invention is based on my observation that, in any given stand of a multi-stand mill, the roll pressure exerted on the bar passing therethrough has a substantially constant relation to the torque exerted on the rolls by the driving motor (assuming a constant voltage applied thereto) unless and until the tension on the bar between said stand and its successor changes. I take advantage of this state of affairs and compare the relative values of roll pressure and motor torque or current, to indicate the degree of interstand tension existing in the bar.

More specifically, I derive a voltage proportional to the rolling pressure by means of load cells and another proportional to the motor current. I employ a differential voltmeter to compare these Voltages and the resulting indication shown thereby signfies the degree of tension then existing.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illustrating the present preferred embodiment. The single figure of the drawing is a diagram illustrating my invention as applied to two successive stands of a multi-stand mill for hot-rolling strip, e.g., the first two stands of a six-stand finishing mill.

Referring now in detail to the drawing, the first stand of a continuous mill indicated generally at 10, comprises working rolls 11 driven by a motor 12 and backing rolls 13. A shunt 14 in circuit with the motor armature provides a voltage proportional to the motor current and therefore the torque exerted by the motor. Load cells 15 (Pressductor cells of ASEA Electric, Inc., 500 Fifth Avenue, New York, NY.) under the necks of the bottom backing roll give a voltage proportional to the rolling pressure exerted by the rolls on a strip bar B when it is introduced therebetween. The output of cells 15 is supplied to a balancing and matching network 16 (ASEA Catalog No. TMPA 101) connected between them and a differential voltmeter 17 in series with potentiometers 19 and 19a. Voltmeter 17 may be that manufactured by 3,228,241 Patented Jan. 11, 1966 General Electric Co. and includes a zero-center indicator 18. Potentiometers 19 and 19a pennit adjustments to be made to compensate, respectively, for the voltage applied to the motor 13 and the precent reduction effected in the first stand.

The second stand 20 is provided with the identical equipment described above for the first stand, corresponding elements being designated by the same reference numerals primed. The remaining stands of the mill, usually four, are also similarly equipped. The functioning of the invention will be made clear in the following explanation. It will be assumed that potentiometers 19 and 19a have been properly adjusted so that the indicator 18 of voltmeter 17 initially reads zero.

As bar B (which has been preliminarily reduced by roughing stands of the mill, not shown) enters the rolls 11 of the first finishing stand, the current through motor 12 required for rolling produces an increase in the voltage across shunt 14 and the roll pressure produces a proportional signal from cells 15. Potentiometer 19 having been set to compensate for motor voltage and potentiometer 19a for the percent reduction in the first stand 10, voltmeter 17 compares these signals and causes the difference to appear on indicator 18. If the adjustments of potentiometers 19 and 19a are correct, then the indicator will remain in the center indicating zero. The strip bar then proceeds to the second stand and enters between rolls 11' thereby producing signals similar to those de scribed for the first stand. If the interstand tension is a minimum or very nearly zero then the indicators for both stand will read zero. If interstand tension is greater than zero then the indicator 18 will deflect to the right (for example) and the indicator 18 will deflect in the opposite direction or to the left. The amount of deflection for both meters will be proportional to the existing interstand tension.

The strip bar 11 next proceeds to the third stand there- 'by producing similar signals in its equipment similar to those described for the first and second stands. If the tension between the second and third stands is a minimum or nearly Zero then the indicator 18" for the third stand will remain at zero indication and the indicators 18 and 18' will remain unchanged. If this interstand tension is greater than zero, however, then the indicator 18" will deflect to the left and indicator 18' will move to the right, or clockwise, essentially a proportional amount. There is a certain amount of tension reflected forward and backward between the several stands as changes occur between pairs of adjacent stands. Such variations in the tension between the several stands will be accurately shown by the voltmeter indicators.

The system shown may be easily tested for the proper setting of potentiometers 19 and 19a by making slight adjustments of motor speeds and observing the effects thereof, assuming the adjustments are made in the direction to decrease the interstand tension.

It will be apparent from the foregoing that the invention provides a simple indicator responsive instantaneous ly, without the necessity of any contact with the bar being rolled.

Although I have disclosed herein the preferred embodiment of my invention, I intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention.

I claim:

1. Apparatus for indicating the tension to which a workpiece being rolled in a continuous rolling mill is subjected between adjacent stands thereof, each having its own driving motor for driving its working rolls, comprising means producing a voltage proportional to the current drawn by the driving motors of said stands, means producing a voltage proportional to the rolling pressure exerted on the workpiece by the working rolls of said stands, means associated with each of said stands for comparing said voltages and means for indicating the result of such comparison.

2. Apparatus as defined in claim 1, characterized by said comparing means being a differential voltmeter.

References Cited by the Examiner UNITED STATES PATENTS Fawkes 7359 Stone 7315,6 X Shayne et a1. 7315.6 Hitchcock et a1. 73-143 Norton 73-443 10 RICHARD C. QUEISSER, Primary Examiner. 

1. APPARATUS FOR INDICATING THE TENSION TO WHICH A WORKPIECE BEING ROLLED IN A CONTINUOUS ROLLING MILL IS SUBJECTED BETWEEN ADJACENT STANDS THEREOF, EACH HAVING ITS OWN DRIVING MOTOR FOR DRIVING ITS WORKING ROLLS, COMPRISING MEANS PRODUCING A VOLTAGE PROPORTIONAL TO THE CURRENT DRAWN BY THE DRIVING MOTORS OF SAID STANDS, MEANS PRODUCING A VOLTAGE PROPORTIONAL TO THE ROLLING PRESSURE EXERTED ON THE WORKPIECE BY THE WORKING ROLLS OF SAID STANDS, MEANS ASSOCIATED WITH EACH OF SAID STANDS 